1. Field of the Invention
The present invention relates to systems and methods for reproducing documents and other files, and in particular to a method and system for the reproduction of grayscales at remote devices such as facsimile machines.
2. Description of the Related Art
Facsimile machines are widely used in business today. Unfortunately, while most documents today are reproduced with a resolution of 300 dots per inch (DPI) or more, transmission bandwidth and other factors limit fax machines to the transmission and reception of images of considerably less resolution, usually in the order of either 204xc3x97196 or 204xc3x9798 DPI. This reduction in image resolution often results in a received transmission that is distorted with Moire patterns, jagged edges on text and images, severely limited dynamic range, reduced contrast and blurred. This can make the faxed document difficult or impossible to read. As a result, high quality documents cannot be transmitted with confidence that they will be reproduced correctly by the receiving facsimile machine.
The present invention discloses a method, apparatus, and an article of manufacture for transmitting data to a presentation device for receiving facsimile transmissions.
According to one embodiment of the invention, the method comprises the steps of receiving a presentation job comprising input data associable with at least one input grayscale value, retrieving at least one of a plurality of threshold matrices, each threshold matrix selected to control a grayscale rendering characteristic of the facsimile presentation device associated with the threshold matrix, applying the grayscale values to the retrieved threshold matrix to rasterize the input data, and transmitting the rasterized input data to the facsimile presentation device. In one embodiment of the present invention, the step of transmitting the rasterized input data to the presentation device comprises the steps of reducing the rasterized input data to an intermediate format being one of a number of widely supported formats, generating device-specific data and device-specific control information for the presentation device based on the intermediate format and control information associated with the input data, and transmitting the device-specific data and the device-specific control information to the presentation device. This invention can be practiced in several embodiments, and permits the user to select the threshold matrix according to the presentation device and/or a selected presentation quality.
According to another embodiment of the invention, the apparatus comprises a means for receiving a presentation job having input data associable with at least one input grayscale value, means for retrieving at least one of a plurality of threshold matrices, each threshold matrix selected to control a grayscale rendering characteristic of the facsimile presentation device associated with the threshold matrix, means for applying the grayscale values to the retrieved threshold matrix to rasterize the input data, and means for transmitting the rasterized input data to the facsimile presentation device. In one embodiment, the apparatus comprises a facsimile machine, and the means for receiving a presentation job comprises a scanner. In another embodiment, the apparatus is comprised of a computer executing software instructions to translate a document, image, or other computer file into rasterized input data for transmission to a presentation device.
The foregoing uses calibration curves and threshold arrays which are specifically designed to enhance the output quality of the facsimile transmission and reproduction, and enable users to provide their outgoing faxes with high quality images and text that can be accepted by a receiving fax machine with the image fidelity intact. The result is that the user is able to transmit higher quality images that are more visually appealing, easier to read, and convey the information content of the original.